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Abstract:

An active reception period (active time) of a power saving pattern (DRX)
is masked to a measurement period (ABS) of a serving or neighbor cell
interference mitigation pattern (eICIC) such that the masked active
reception period repeatedly coincides with the measurement period. Then
the masked active reception period is utilized for communicating resource
allocations (PDCCHs) between a serving cell (eNB) and a user equipment
(UE). In various embodiments: the masking is done without shortening a
sleep opportunity (DRX opportunity) of the power saving pattern; the
masking is implemented by delaying an on-duration start time of the
active reception period; the on-duration start time is controlled by a
timer which runs only during measurement periods of the interference
mitigation pattern, or by applying a second offset generated by the UE in
addition to applying a first offset configured by the serving cell; and
the masking is by adopting a default power saving pattern.

Claims:

1. A method, comprising: masking an active reception period of a power
saving pattern to a measurement period of a serving cell or neighbor cell
interference mitigation pattern such that the masked active reception
period repeatedly coincides with the measurement period; and utilizing
the masked active reception period for communicating resource allocations
between a serving cell and a user equipment.

2. The method according to claim 1, in which the masking is done without
shortening a sleep opportunity of the power saving pattern.

3. The method according to claim 1, in which: the active reception period
of the power saving pattern is an active time of a discontinuous
reception DRX cycle; and the measurement period of the interference
mitigation pattern is an almost-blank subframe ABS of an enhanced
intercell interference coordination eICIC measurement restriction
pattern.

4. The method according to claim 1, in which masking the active reception
period to the measurement period comprises delaying an on-duration start
time of the active reception period.

5. The method according to claim 4, in which the on-duration start time
is controlled by a timer which runs only during measurement periods of
the interference mitigation pattern.

6. The method according to claim 4, in which the on-duration start time
is controlled by applying a second offset generated by the user equipment
executing the method in addition to applying a first offset configured by
the serving cell.

7. The method according to claim 4, in which masking the active reception
period to the measurement period comprises adopting a default power
saving pattern and delaying the on-duration start time of the active
reception period of the default power saving pattern.

8. The method according to claim 1, in which the method is executed by
the user equipment, and utilizing the masked active reception period for
communicating resource allocations comprises the user equipment tuning a
receiver to receive from the serving cell a physical downlink control
channel.

9. The method according to claim 1, in which the method is executed by
the serving cell, and utilizing the masked active reception period for
communicating resource allocations comprises the serving cell
transmitting to the user equipment a physical downlink control channel.

10. An apparatus comprising at least one processor; and at least one
memory including computer program code; in which the at least one memory
and the computer program code is configured, with the at least one
processor, to cause the apparatus at least to perform: masking an active
reception period of a power saving pattern to a measurement period of a
serving cell or neighbor cell interference mitigation pattern such that
the masked active reception period repeatedly coincides with the
measurement period; and utilizing the masked active reception period for
communicating resource allocations between a serving cell and a user
equipment by either sending the resource allocations to the user
equipment or receiving the resource allocations from the serving cell.

11. The apparatus according to claim 10, in which the masking is done
without shortening a sleep opportunity of the power saving pattern.

12. The apparatus according to claim 10, in which: the active reception
period of the power saving pattern is an active time of a discontinuous
reception DRX cycle; and the measurement period of the interference
mitigation pattern is an almost-blank subframe ABS of an enhanced
intercell interference coordination eICIC measurement restriction
pattern.

13. The apparatus according to claim 10, in which masking the active
reception period to the measurement period comprises delaying an
on-duration start time of the active reception period.

14. The apparatus according to claim 13, in which the on-duration start
time is controlled by a timer which runs only during measurement periods
of the interference mitigation pattern.

15. The apparatus according to claim 13, in which the on-duration start
time is controlled by applying a second offset generated by the user
equipment in addition to applying a first offset configured by the
serving cell.

16. The apparatus according to claim 13, in which masking the active
reception period to the measurement period comprises adopting a default
power saving pattern and delaying the on-duration start time of the
active reception period of the default power saving pattern.

17. A memory tangibly storing a computer program that is executable by at
least one processor, in which the computer program comprises: code for
masking an active reception period of a power saving pattern to a serving
cell or neighbor cell measurement period of an interference mitigation
pattern such that the masked active reception period repeatedly coincides
with the measurement period.

18. The memory according to claim 17, in which the active reception
period of the power saving pattern is an active time of a discontinuous
reception DRX cycle; and the measurement period of the interference
mitigation pattern is an almost-blank subframe ABS of an enhanced
intercell interference coordination eICIC measurement restriction
pattern.

19. The memory according to claim 17, in which masking the active
reception period to the measurement period comprises delaying an
on-duration start time of the active reception period.

20. The memory according to claim 19, in which: the on-duration start
time is controlled by a timer which runs only during measurement periods
of the interference mitigation pattern; or the on-duration start time is
controlled by applying a second offset generated by a user equipment in
addition to applying a first offset configured by a network; or masking
the active reception period to the measurement period comprises adopting
a default power saving pattern and delaying the on-duration start time of
the active reception period of the default power saving pattern.

Description:

TECHNICAL FIELD

[0001] The exemplary and non-limiting embodiments of this invention relate
generally to wireless communication systems, methods, devices and
computer programs and, more specifically, relate to aligning in time a
power saving schedule such as a UE's DRX and an interference suppression
schedule such as almost blank subframes of an eICIC arrangement.

BACKGROUND

[0002] The following abbreviations that may be found in the specification
and/or the drawing figures are defined as follows:

[0003] 3GPP third
generation partnership project

[0004] ABS almost blank subframe

[0005] CA
carrier aggregation

[0006] CE control element

[0007] CQI channel quality
indicator

[0008] CRS common reference signal

[0009] DRX discontinuous
reception period

[0010] DL downlink

[0011] E-UTRA evolved universal
terrestrial radio access

[0012] eICIC enhanced inter-cell interference
coordination

[0013] eNB evolved NodeB (base transceiver station in
LTE/LTE-A)

[0014] HARQ hybrid automatic repeat request

[0015] LTE long
term evolution (evolved UTRAN)

[0016] LTE-A LTE-advanced

[0017] MAC
medium access control

[0018] PDCCH physical downlink control channel

[0019] PDSCH physical downlink shared channel

[0020] PHY physical
(logical layer)

[0021] PUSCH physical uplink shared channel

[0022] RLM
radio link measurements

[0023] RRC radio resource control

[0024] RRM
radio resource measurements

[0025] RSRP reference signal received power

[0026] RTT round trip time

[0027] UE user equipment

[0028] UL uplink

[0029] Various different wireless radio access technologies specify
procedures which are primarily directed toward managing power consumption
in user devices which have a limited power supply (for example,
galvanic/battery or fuel cell). LTE Release 8 includes the concept of
DRX, a per-UE schedule known to both the network and the UE by which the
network schedules it DL signaling of radio resource allocations which are
relevant to a specific UE only within a certain active window of that
UE's DRX cycle. This enables the UE to periodically go to sleep instead
of listening continuously for scheduling commands. The purpose of the DRX
concept is to improve the UE's energy efficiency; since any given UE
typically is not scheduled continuously there would be some natural
periods of inactivity. By scheduling periodic inactivity periods the eNB
allows the UE to de-power some of its hardware and ongoing processing and
thereby extend the time over which the UE's limited power source is
sufficient.

[0030] In general the DRX mechanism uses a periodic DRX cycle that is
composed of two fixed parts: an active part and a sleep part. The active
part, which LTE terms Active time, is when the UE is to be `awake` and
actively listening to see if the network is sending a PDCCH which
schedules the UE for DL and/or UL radio resources. The sleep part, which
TE terms the DRX opportunity, is the time the UE might be able to operate
in a reduced-power/sleep mode (but there may at times be some scheduled
radio resources or ongoing HARQ processes that extends into the DRX
opportunity). The convention in LTE at least is that the DRX cycle always
begins with an active part, followed by the sleep part after which the
cycle begins anew. For the cases noted above in which a scheduled
resource or some HARQ process keeps the UE from entering its sleep mode
at the usual time given by the DRX cycle, the UE simply extends the
active part and correspondingly reduces its sleep part so the next DRX
cycle begins on time.

[0031] The UE and the network have timers to track the DRX. In LTE the
network configures the specific DRX cycle (length, start times) for the
UEs. For example, a long DRX might be DRX cycle=640 ms; on duration=10
ms; inactivity timer=5 ms. This DRX configuration would reduce the
nominal activity time for the UE to 1/64, (1.56%) as compared to
continuous active DL reception or listening. Other radio access
technologies use a similar concept which allows the UE to functionally
`sleep` for purposes of extending the time over which the radio can
operate from its limited power supply. In theory and practice the DRX
enables the UE to remain in a power saving mode for most of the time
outside heavy activity periods where UE is scheduled continuously.

[0032] LTE Release 10 (LTE-A) uses carrier aggregation, in which the whole
system bandwidth is divided into multiple component carriers. Since LTE-A
contemplates many more network access nodes of various varieties (for
example, conventional cells termed macro cells, pico/femto cells/home
eNBs, remote radioheads and repeaters) it has also introduced a mechanism
to mitigate interference among them, termed enhanced inter-cell
interference coordination eICIC. In this technique one cell coordinates
with its neighbor cells to avoid interfering transmissions. One aspect of
eICIC in LTE Release 10 is almost-blank subframes (ABS), in which a
network node transmits nothing except the common reference signals used
for measurements (and in some cases also essential control information
like synchronization, paging, or system information) but never any
unicast DL user data.

[0033] In general an eNB transmits its ABSs according to a known pattern
and the transmission of the eNB during the ABSs should cause little if
any interference to transmissions of neighboring eNBs. The eICIC concept
is used for both macro and pico/femto eNBs. A femto eNB may coordinate
its transmissions with the overlay macro eNB in order to allow macro user
devices close to the femto eNB to experience less interference during the
femto eNB's ABS transmissions. Or a macro eNB coordinates its own ABS
transmissions with a nearby pico eNB so that the smaller interference
from the macro eNB's ABSs allows user devices within a larger area to
find and connect to the pico eNB. The ABSs in these coordinated patterns
are sent with CRSs, which the user devices use for channel measurement
purposes. When eICIC is in use the user device may be instructed to
restrict its measurements of the serving cell or of neighbor cells to the
configured ABSs. It is also possible to limit the serving cell and
neighbor cell measurements according to different patterns.

[0034] So the DRX and the eICIC serve widely different purposes: DRX is
needed for conserving UE power and is coordinated between the UE and its
serving network node; eICIC is needed for making RLM measurements of
serving cell and RRM measurements of serving and neighbor cells for
handover purposes (for example, RLM measurement restrictions may be used
when a small cell and the macro cell interfere with each other and macro
cell user is close to the small cell but not able to access the small
cell) and is coordinated between adjacent network nodes. It follows that
these two procedures are not linked in any way and the inventors see no
such linking in the relevant specifications for LTE and LTE-A. The
inventors have identified that the eICIC may operate to drastically limit
the power savings that the DRX concept enables for a UE. The below
teachings restore at least some of the potential power savings at the UE
when the DRX is imposed in the presence of measurement restriction
patterns due to ABS.

SUMMARY

[0035] The foregoing and other problems are overcome, and other advantages
are realized, by the use of the exemplary embodiments of this invention.

[0036] In a first exemplary embodiment of the invention there is a method
comprising: masking an active reception period of a power saving pattern
to a measurement period of the serving cell or a neighbor cell
interference mitigation pattern such that the masked active reception
period repeatedly coincides with the measurement period; and utilizing
the masked active reception period for communicating resource allocations
between a serving cell and a user equipment.

[0037] In a second exemplary embodiment of the invention there is an
apparatus comprising at least one processor; and at least one memory
including computer program code. In this embodiment the at least one
memory and the computer program code is configured, with the at least one
processor, to cause the apparatus at least to perform: masking an active
reception period of a power saving pattern to a serving or neighbor cell
measurement period of an interference mitigation pattern such that the
masked active reception period repeatedly coincides with the active
measurement period; and utilizing the masked active reception period for
communicating resource allocations between a serving cell and a user
equipment. For the case in which the apparatus is a serving cell (or one
or more components thereof) this communicating of the resource
allocations comprises sending the resource allocations to the user
equipment; for the case in which the apparatus is a user equipment (or
one or more components thereof) this communicating of the resource
allocations comprises receiving the resource allocations from the serving
cell.

[0038] In a third exemplary embodiment of the invention there is a
computer readable memory tangibly storing a computer program that is
executable by at least one processor. In this embodiment the computer
program comprises code for masking an active reception period of a power
saving pattern to the serving or a neighbor cell measurement period of an
interference mitigation pattern such that the masked active reception
period repeatedly coincides with the measurement period.

BRIEF DESCRIPTION OF THE DRAWINGS

[0039] FIG. 1A is a prior art variable for masking transmission of CQI
reports according to a DRX cycle as set forth at 3GPP TS 36.321 v10.2.0
(2011-06) and 36.133 v10.3.0 (not yet complete).

[0040] FIG. 1B is a prior art table 8.1.2.8.1.2-1 from 3GPP TS 36.133
v10.3.0 which gives the current time restrictions for identifying a newly
detectable FDD intra-frequency cell during the DRX.

[0041]FIG. 2 is a plan view of a conceptual radio environment in which
the various exemplary embodiments may be practiced to advantage.

[0042] FIG. 3 is a schematic timing diagram of a DRX cycle and its
adjustment according to certain embodiments of these teachings to assure
an overlap among active periods of the adjusted DRX cycle and ABSs of the
eICIC pattern.

[0043]FIG. 4 is a logic flow diagram illustrating the operation of a
method, and a result of execution of computer program instructions
embodied on a computer readable memory, for practicing exemplary
embodiments of these teachings.

[0044]FIG. 5 is a simplified block diagram of some of the devices shown
at FIG. 2 which are exemplary electronic devices suitable for use in
practicing the exemplary embodiments of this invention.

DETAILED DESCRIPTION:

[0045] When the DRX procedure was designed for LTE Release 8, the UE was
expected to do its measurements only during the Active time. But
introducing eICIC in LTE Release-10 means that some or all of the ABS
occasions where the UE is instructed to do measurements by the eICIC
configuration may fall outside the Active times of the DRX cycle. When
this occurs the UE may have to stay awake longer than necessary in order
to take its channel measurements in the ABSs which carry the CRSs,
meaning the DRX performance is degraded significantly. The eICIC, which
gives measurement restriction patterns for the UE to take its RLIWRRM
measurements and whose specifications were drawn up after those for the
DRX, may assume that there will be at least one such ABS occasion during
the DRX Active time but there is no mechanism to assure this outcome.
Typically the measurement periods of the eICIC coincide with the ABSs.
While in some cases happenstance may align the ABS with the active period
of the DRX active time, these teachings detail various exemplary ways to
positively assure that outcome. Briefly, when the DRX and eICIC are used
together, the DRX active time is masked according to the measurement
restriction pattern (which is more generally termed a serving or neighbor
cell interference mitigation pattern). The result is that the UE is
allowed to wake up only when there is time alignment between the DRX
Active time and an ABS.

[0046] There are some prior art uses of masking for the DRX. For example,
the UE's transmissions of CQI reports can be masked according to its DRX
Active time pattern. FIG. 1 shows the variable cqi-Mask-r9 which is in
3GPP RRC specification TS 36.133. This variable cqi-Mask-r9 is defined
such that when used, the UE is required to send CQI/PMI/RI reports only
during the Active time of the DRX cycle, never during the DRX
opportunity.

[0047] FIG. 1B is a prior art table 8.1.2.8.1.2-1 taken from the LTE
Release 10 radio resource management requirements at 3GPP TS 36.133
v10.3.0 (note that this version of the specification is incomplete for
some Rel'10 content as of this writing) which gives the current time
restrictions for identifying a newly detectable FDD intra-frequency cell
during the DRX. That same specification also provides that for
eICIC-restricted measurements during the DRX: "The time domain
measurement resource restriction pattern configured for the measured cell
indicates at least one subframe per radio frame for performing the RSRP
measurement." This means that for the measurements to be possible, the UE
has to have at least one measurement occasion for each 10 ms. The cell
identification requirements are expected to allow the UE more time to
detect a cell when UE is utilizing both eICIC and DRX than when UE is
only utilizing DRX or eICIC.

[0048] In accordance with an exemplary embodiment, when DRX and eICIC are
used together the DRX Active time is masked according to the given
measurement restriction pattern(s). This means that the UE is allowed to
wake up only during those times when the ABSs and the Active times match.
These teachings are not limited only to the LTE-A system though. Since
other radio access technologies may use different terminology for the
concepts of DRX and eICIC, more generalized terms are power saving
pattern and inter-cell interference mitigation pattern, respectively. In
that regard the exemplary embodiments detailed further below mask an
active reception period of a power saving pattern to an active
measurement period of an inter-cell interference mitigation pattern such
that the active reception period repeatedly coincides with the active
measurement period. The term `repeatedly` is used to show a purposeful
act to assure the active periods coincide rather than an occasional
overlap which might occur by happenstance if there is no operational
linkage between these patterns.

[0049] In certain embodiments below, this masking is done without
shortening a sleep opportunity (the DRX opportunity in LTE terminology)
of the power saving pattern. This is not to say the DRX opportunity is
always fully preserved; it may be that there is a scheduled PDSCH or
PUSCH, which are allocated to the UE in a PDCCH sent during its active
time, which extend into the UE's DRX opportunity. Or there may be a HARQ
process which extends a re-transmission into the UE's DRX opportunity.
Those conventional instances may still occur; the relevant point is that
in certain embodiments where the DRX opportunity is not shortened it is
not shortened due to masking the DRX active period to the eICIC pattern.

[0050] Before detailing the various embodiments for how these patterns can
be conformed to one another to achieve the coinciding active periods
noted above, reference is made to FIG. 2 for illustrating an exemplary
radio environment in which these teachings can be practiced to advantage.
There is a UE 20 operating in the vicinity of a macro eNB 22 and a femto
eNB 26. The typical case for eICIC is that only the femto eNB 26 is
utilizing an eICIC pattern and the UE 20, attached to the macro eNB 22,
will receive its resource allocations (PDCCHs) from its serving macro eNB
22 during the active time of its DRX. That same UE 20 can take neighbor
cell measurements of the femto eNB 26 for mobility purposes by reading
the CRS in the ABS transmitted by the femto eNB 26, and report that
measurement back to its serving macro eNB 22. Embodiments of these
teachings align this UE's DRX active time from the macro eNB 22 with the
ABS of the femto eNB 26. This assures the UE 20 operating near the femto
eNB 26 and attached to the macro eNB 22 that the femto eNB 26 will not
interfere with any PDCCHs the macro eNB 22 sends to the UE 20. Since the
femto eNB 26 transmits CRSs both inside and outside the ABSs, the UE 20
can take measurements of the neighbor femto eNB 26 outside the ABSs if it
is unable to do so during the overlapped DRX active time and ABS.

[0051] It may be that the macro eNB 22 is transmitting ABSs for eICIC and
not the pico eNB 26. An example of this has the UE 20 attached to the
pico eNB 26, near the cell edge and ready for handover to the macro eNB
22 but the macro eNB 22 wants to retain the UE 20 connected to the pico
eNB 26. In this case the macro eNB 22 can use its ABS to protect the pico
eNB 26 so that the UE 20 only measures its serving pico eNB 26 during the
ABSs of the macro eNB 22. The UE's signal strength with the pico eNB 26
will remain high since the macro eNB's ABSs cause little interference
when the UE 20 measures its serving cell 26, and so a handover is not yet
triggered. In this case, embodiments of these teachings have the UE 20
align the DRX active time from the pico eNB 26 with the ABS of the macro
eNB 22. The UE 20 will take its neighbor measurements of the macro eNB 22
by reading CRSs transmitted by the macro eNB 22 which may be within or
outside of the macro eNB's, according to the UE's best opportunity.

[0052] Now consider the timing diagram of FIG. 3 which spans two radio
frames; frame n and a portion of frame n+1. Subframes of these frames are
annotated as sf0, sf1, sf2, etc. There is shown an eICIC measurement
restriction pattern 320 for the pico eNB 22 with an ABS 323 (the UE's
restricted measurement period) only at sf8 of frame n. This example is
not limiting as it may be the macro eNB which has the eICIC measurement
restriction pattern which gives measurement occasions for the UE.

[0053] There is a first DRX pattern 300 having an active time 303A
spanning only sf4, sf5 and sf6 of frame n, and DRX opportunities 302B,
303B in all other illustrated subframes. Assume this first DRX pattern
300 is the one which the serving macro eNB 22 has configured for the UE
20 according to conventional practice. Since the DRX cycle 300 begins
with an active period, active time 303A and DRX opportunity 303B are
within the same cycle and DRX opportunity 302B is residual from a
previous iteration of the same cycle 300. The active period 303A of the
first DRX pattern 300 does not coincide with the ABS 323 of the eICIC
measurement restriction pattern 320 of the pico eNB 26, and so in this
conventional arrangement the UE 20 which enters sleep mode after subframe
6 according to its DRX opportunity 303B would need to wake again for the
ABS 323 in subframe 8.

[0054] In a general case, it might be possible for the UE to sleep during
the intervening subframes between the ABS 333, but in this particular
example case the sleep time would consist of only a single subframe sf7,
which might not allow any power saving for the UE since turning a
receiver on/off also requires some (small) time which might be consumed
entirely during sf7. So in the FIG. 3 example with the first DRX pattern
300 the UE 20 would likely extend the time it stays fully powered up to
subframe 8, effectively extending its DRX active time 303A and reducing
the time it has for powering down in the DRX opportunity 303B.

[0055] In the example above, the DRX active period is not masked to the
ABS but the UE 20 may simply extend the time it stays awake after the
active time 303A to overlap it, which results in a reduction to the
DRX/sleep opportunity 303B. Below are three non-limiting embodiments of
masking the DRX active period to the ABS to assure the DRX active time
overlaps with the relevant ABS 323 while preserving the potential for
more sleep time at the UE.

[0056] In a first embodiment the UE wakes up from its DRX opportunity only
if an ABS measurement subframe coincides with the Active time. Otherwise,
the UE shall continue the DRX opportunity until such time when it can
determine that there will be a measurement subframe during an Active
time. In one implementation of this first embodiment the UE 20 continues
its DRX opportunity until there is an active time coinciding with an ABS.
With reference to FIG. 3, if we consider the second DRX pattern 310 as
merely a different cycle of the first DRX pattern 300 but overlaid on
different frames, a UE 20 seeing the DRX active time 303A align as shown
for DRX cycle 300 would not wake as scheduled at t1 for its active time
303A since there is no overlap with an ABS 323, but when the DRX active
time 313A aligns as shown for cycle 310 the UE 20 would wake at time t3
since the ABS 323 overlaps. In the cycle 300 the UE 20 would simply
continue in sleep mode until a cycle 310 arises in which there is an
overlap between the ABS 323 and the DRX active time as the network
configured that DRX for the UE 20, without making any adjustments of its
own to that configured DRX pattern.

[0057] Another implementation of this first embodiment uses something less
than the full masking of the first implementation. In this case, instead
of the UE 20 retaining the network-configured DRX start time at t1 and
sf5, it would postpone the DRX active time on-duration start time until
there was an overlap of the active time and the ABS. FIG. 3 illustrates
two examples of the UE 20 with DRX pattern 300 and needing to overlap its
active time with the ABS 323. If the understanding between the UE 20 and
its serving node (macro eNB 22 in this example) is that the DRX active
period will begin only when there is an ABS, then the result is shown as
the second DRX pattern 310 at FIG. 3; the start of the active time 313A
on-duration is delayed from t1 to t3 so that the ABS aligns with the
first subframe of the active time 313A and the network-configured
duration of the active time 313A is retained. In FIG. 3 this is an offset
340 of four subframes and the network-configured active time duration is
three subframes. If the understanding between the UE 20 and its serving
node is that the last subframe of the DRX active period will be aligned
to the ABS, then the start of the active time 303A on-duration of the
network-configured DRX will in FIG. 3 be delayed from t1 to t2 and the
active time duration will run from t2 to t4. In FIG. 3 this is an offset
of two subframes. So long as there is a common understanding how the
alignment is to occur, any subframe of the active time (first, last, or
some other subframe of the active time) can be masked to the ABS. In both
these examples, the UE 20 would operate with the DRX cycle which the
network configured for it so long as there is no eICIC in operation, but
anytime there is an operative eICIC the UE 20 would mask the active time
303A as detailed in the above examples.

[0058] One way to implement this postponement of the active time
on-duration is with a new DRX timer, which we term for convenience
ABSTimer. This ABSTimer is started when the current subframe is an ABS
subframe according to the UE-configured pattern, and stopped when the
current subframe is not an ABS subframe according to the UE-configured
pattern. So using the FIG. 3 example the new ABSTimer runs only during
sf8 among all of the illustrated subframes. For the LTE-A system, the
specifications for the DRX process description could then be modified
from that currently at 3GPP TS 36.321 v.10.2.0, section 5.7:
Discontinuous Reception (DRX) to read as follows, in which the italicized
portions are added herein (`measurement subframe` refers to the ABS):

[0059] When a DRX cycle is configured, the Active Time includes the time
while:

[0060] ABSTimer is not running and (onDurationTimer or
drx-InactivityTimer or drx-RetransmissionTimer or
mac-ContentionResolutionTimer (as described in subclause 5.1.5) is
running); or

[0061] When DRX is configured, the UE shall for each subframe:

[0062] if
the current subframe is a measurement subframe according to configured
MeasSubFramePattern:

[0063] stop the ABSTimer.

[0064] else:

[0065] start
the ABSTimer.

[0066] if a HARQ RTT Timer expires in this subframe and the
data in the soft buffer of the corresponding HARQ process was not
successfully decoded:

[0067] The second embodiment is similar in result to the on-duration
postponement of the first embodiment, but instead of a new timer the
start of the active time on-duration is postponed until the next
available measurement/ABS subframe (as indicated by the eICIC measurement
pattern) by changing the DRX Offset parameter each time the active time
on-duration is postponed. The DRX Offset parameter is one of the DRX
configuration parameters which the network provides to the UE 20. The DRX
offset could be changed according to a (semi-static) set of rules, for
example so that UE would ensure that the ABS occasion happens at the
first or last subframe of the active time on duration.

[0068] Since the second embodiment in which the UE 20 modifies the result
of applying the DRX Offset parameter might lead to a mismatch between the
UE 20 and the eNB 22, 26, in a particular but non-limiting implementation
the UE 20 will periodically signal the change it makes to the DRX Offset
back to its serving eNB. In various implementations the UE 20 sends this
signaling via a MAC control element, or via PHY signaling, or via RRC
signaling. This change to the DRX Offset parameter is shown in FIG. 3 as
the additional offset 340. Similar to the postponement detailed in the
first embodiment, the above examples have the offset 340 as two subframes
or up to four subframes, depending on the UE and eNB's common
understanding of which portion of the (postponed) active time 303A is to
align with the ABS 323. In other implementations the UE need not signal
the change and its serving eNB can simply track what the active time
alignment will be since the eNB knows its neighbor cell eICIC patterns as
well as the DRX it configured for the UE.

[0069] One way to implement the postponement of the active time
on-duration according to the second embodiment is with a new DRX
parameter ABSOffset that is applied on top of the existing drxStartOffset
as follows:

[0070] If the Short DRX Cycle is used and
[(SFN*10)+subframe number] modulo
(shortDRX-Cycle)=(drxStartOffset+ABSOffset) modulo (shortDRX-Cycle); or

[0071] if the Long DRX Cycle is used and [(SFN*10)+subframe number]
modulo (longDRX-Cycle)=drxStartOffset+ABSOffset:

[0072] start
onDurationTimer.

[0073] The ABSOffset parameter would be set when the DRX start is
extended. In this case the offset 340 represents the ABSOffset since it
is applied over the network-configured DRX Offset value.

[0074] In a third embodiment, anytime the DRX and the eICIC are both used,
the DRX is automatically matched to the measurement restriction pattern
(or patterns if the UE is utilizing measurement restriction patterns for
multiple network nodes). For example, once the UE with a configured DRX
cycle sees that eICIC is made operational in a cell, the UE will
automatically change its DRX cycle to 40ms, with the on-duration of the
active time modified to occur at each measurement occasion according to
the signaled serving cell and neighbor cell measurement restriction
patterns. In case there are multiple separated measurement occasions
within the measurement restriction pattern, the UE would wake up at every
such occasion. In this example the short DRX cycle (if configured) is
also set to 40 ms, effectively disabling it, but other DRX parameters
signaled by the network to the UE stay unchanged. The 40ms DRX cycle is
specific for an LTE-A implementation; more generally there is a default
power saving cycle length which the UE adopts in this third embodiment.
If at some time eICIC measurement restrictions are disabled for this UE,
the DRX cycle and on-duration values revert back to those given by the
DRX parameters which the network signaled when first configuring the DRX
for the UE.

[0075] This third embodiment may be implemented with a new absDRX-Cycle
variable which the UE uses as follows:

[0076] if drx-InactivityTimer
expires or a DRX Command MAC control element is received in this
subframe:

[0077] if the absDRX-Cycle is configured:

[0078] use the
absDRX-Cycle;

[0079] else if the Short DRX cycle is configured:

[0080]
start or restart drxShortCycleTimer;

[0081] use the Short DRX Cycle.

[0082] else:

[0083] use the Long DRX cycle.

[0084] if
drxShortCycleTimer expires in this subframe and absDRX-Cycle is not
configured:

[0085] use the Long DRX cycle.

[0086] if UE has either
measSubframePatternPCell or MeasSubframePatternConfigNeigh-r10 for PCell
frequency configured:

[0087] use Long DRX Cycle according to value sf40
and set absDRX-Cycle to contain "1" for each occurrence of "1" in the IE
measSubframePatternP Cell or IE measSubframePatternConfigNeigh-r10 for
the PCell frequency.

[0088] if the absDRX-Cycle is used and contains
"1" at position [(SFN*10)+subframe number] modulo 40

[0089] start
onDurationTimer.

[0090] if the absDRX-Cycle is used and contains "0" at
position [(SFN*10)+subframe number] modulo 40

[0091] stop
onDurationTimer.

[0092] One technical effect of these teachings is that they enable a more
efficient use of DRX when eICIC is used at the same time. These
embodiments are straightforward too implement because they are compatible
with existing DRX and eICIC procedures with only minor adaptation.

[0093]FIG. 4 is a logic flow diagram which may be considered to
illustrate the operation of a method, and a result of execution of a
computer program stored in a computer readable memory, and a specific
manner in which components of an electronic device are configured to
cause that electronic device to operate. The various blocks shown in each
of FIG. 4 may also be considered as a plurality of coupled logic circuit
elements constructed to carry out the associated function(s), or specific
result of strings of computer program code stored in a memory.

[0094] Such blocks and the functions they represent are non-limiting
examples, and may be practiced in various components such as integrated
circuit chips and modules, and that the exemplary embodiments of this
invention may be realized in an apparatus that is embodied as an
integrated circuit. The integrated circuit, or circuits, may comprise
circuitry (as well as possibly firmware) for embodying at least one or
more of a data processor or data processors, a digital signal processor
or processors, baseband circuitry and radio frequency circuitry that are
configurable so as to operate in accordance with the exemplary
embodiments of this invention.

[0095]FIG. 4 details particular exemplary embodiments of the invention
from the perspective of the UE or of the pico/femto or macro eNB
(whichever is the serving cell) which also tracks the UE's active times
and DRX opportunities to know when it may send a PDCCH. FIG. 4 may be
implemented by the entire UE/eNB or by one or more components thereof,
more generally termed an apparatus. At block 402 of FIG. 4 the
UE/eNB/apparatus masks an active reception period of a power saving
pattern to a serving cell or neighbor cell measurement period of an
interference mitigation pattern such that the masked active reception
period repeatedly coincides with the measurement period. Then at block
404 the apparatus utilizes the masked active reception period for
communicating resource allocations between a serving cell and a user
equipment.

[0096] For the case FIG. 4 is implemented by a UE, the utilizing and
communicating at block 404 may be implemented by receiving PDCCHs from a
serving cell. For the case FIG. 4 is implemented by an eNB or other
network access node, the utilizing and communicating at block 404 may be
implemented by sending PDCCHs to a user equipment. For the LTE-A examples
above, the active reception period of the power saving pattern is an
active time of a discontinuous reception DRX cycle, and the measurement
period of the interference mitigation pattern is an almost-blank subframe
ABS of an enhanced intercell interference coordination eICIC measurement
restriction pattern.

[0097] Further portions of FIG. 4 are optional and may or may not be
combined with one another in various embodiments. Block 406 describes
certain embodiments in which the masking of block 402 is done without
shortening a sleep opportunity of the power saving pattern.

[0098] Block 408 details that masking the active reception period to the
measurement period comprises delaying an on-duration start time of the
active reception period. Block 410 gives the three embodiments above for
how the delay of block 408 might be implemented:

[0099] the on-duration
start time is controlled by a timer which runs only during measurement
periods of the interference mitigation pattern; or

[0100] the on-duration
start time is controlled by applying a second offset generated by a user
equipment in addition to applying a first offset configured by a network;
or

[0101] the masking of block 402 comprises adopting a default power
saving pattern and delaying the on-duration start time of the active
reception period of the default power saving pattern.

[0102] Reference is now made to FIG. 5 for illustrating a simplified block
diagram of various electronic devices and apparatus that are suitable for
use in practicing the exemplary embodiments of this invention. In FIG. 5
there is a first network access node/macro eNB 22 coupled via an X2
interface 27 to a second network access node/pico eNB 26 (or some other
type of interface 27 if the second network access node is a femto eNB),
which are adapted for communication over respective wireless links 21, 23
with an apparatus 20 such as mobile terminals or termed more generally as
a user equipment UE. The macro eNB 22 may be further communicatively
coupled via link 25 to further networks (e.g., a publicly switched
telephone network PSTN and/or a data communications network/Internet),
possibly via a higher network node such as a mobility management
entity/serving gateway MME/S-GW 24 in the case of the LTE system.

[0103] The UE 20 includes processing means such as at least one data
processor (DP) 20A, storing means such as at least one computer-readable
memory (MEM) 20B storing at least one computer program (PROG) 20C,
communicating means such as a transmitter TX 20D and a receiver RX 20E
for bidirectional wireless communications with the macro eNB 22 and with
the pico/femto eNB 26 via one or more antennas 20F. Within the memory 20B
of the first UE 20 is also a computer program for masking the active
period of the DRX to the ABSs of the eICIC measurement restriction
pattern as is detailed above in various embodiments.

[0104] The macro eNB 22 also includes processing means such as at least
one data processor (DP) 22A, storing means such as at least one
computer-readable memory (MEM) 22B storing at least one computer program
(PROG) 22C, and communicating means such as a transmitter TX 22D and a
receiver RX 22E for bidirectional wireless communications with its
associated user devices 20 via one or more antennas 22F and a modem. The
macro eNB 22 also has stored in its memory at 22G software to also mask
the UE's DRX active period to the ABSs of the eICIC measurement
restriction pattern so as to track when the UE is awake and when it is in
sleep mode. The pico/femto eNB 26 is similarly functional with blocks
26A, 26B, 26C, 26D, 26E, 26F and 26G.

[0105] For completeness the MME/S-GW 24 is also shown to include a DP 24A,
and a MEM 24B storing a PROG 24C, and additionally a modem 24H for
communicating with at least the macro eNB 22. While not particularly
illustrated for the UE 20 or eNBs 22, 26, those devices are also assumed
to include as part of their wireless communicating means a modem which
may in one exemplary but non limiting embodiment be inbuilt on an RF
front end chip so as to carry the respective TX 20D/22D/26D and RX
20E/22E/26E.

[0106] At least one of the PROGs 20C, 22C, 26C in the UE 20 and in the
macro and pico/femto eNBs 22, 26 is assumed to include program
instructions that, when executed by the associated DP 20A, 22A, 26A,
enable the device to operate in accordance with the exemplary embodiments
of this invention as detailed more fully above. In this regard the
exemplary embodiments of this invention may be implemented at least in
part by computer software stored on the MEM 20B, 22B, 26B which is
executable by the DP 20A, 22A, 26A of the respective devices 20, 22, 26;
or by hardware; or by a combination of tangibly stored software and
hardware (and tangibly stored firmware). Electronic devices implementing
these aspects of the invention need not be the entire UE 20, or macro eNB
22, or pico/femto eNB 26, but exemplary embodiments may be implemented by
one or more components of same such as the above described tangibly
stored software, hardware, firmware and DP, or a system on a chip SOC or
an application specific integrated circuit ASIC or a digital signal
processor DSP or a modem or a subscriber identity module commonly
referred to as a SIM card.

[0107] Various embodiments of the UE 20 can include, but are not limited
to: cellular telephones; data cards, USB dongles, personal portable
digital devices having wireless communication capabilities including but
not limited to laptop/palmtop/tablet computers, digital cameras and music
devices, and Internet appliances.

[0108] Various embodiments of the computer readable MEM 20B, 22B, 26B
include any data storage technology type which is suitable to the local
technical environment, including but not limited to semiconductor based
memory devices, magnetic memory devices and systems, optical memory
devices and systems, fixed memory, removable memory, disc memory, flash
memory, DRAM, SRAM, EEPROM and the like. Various embodiments of the DP
20A, 22A, 26A include but are not limited to general purpose computers,
special purpose computers, microprocessors, digital signal processors
(DSPs) and multi-core processors.

[0109] Various modifications and adaptations to the foregoing exemplary
embodiments of this invention may become apparent to those skilled in the
relevant arts in view of the foregoing description. While the exemplary
embodiments have been described above in the context of the LTE and LTE-A
systems, it should be appreciated that the exemplary embodiments of this
invention are not limited for use with only this one particular type of
wireless communication system, and that they may be used to advantage in
other wireless communication systems such as for example UTRAN, WCDMA and
others as adapted for power saving active/sleep periods for a UE.

[0110] Some of the various features of the above non-limiting embodiments
may be used to advantage without the corresponding use of other described
features. The foregoing description should therefore be considered as
merely illustrative of the principles, teachings and exemplary
embodiments of this invention, and not in limitation thereof.

Patent applications by Tero Henttonen, Espoo FI

Patent applications by Renesas Mobile Corporation

Patent applications in class Transmission power control technique

Patent applications in all subclasses Transmission power control technique